If you’re using an Azure App Service on a tier that offers staging slots (standard and above) then you might want to consider what happens when you swap a slot.
If you’ve configured a slot then you’ll want to swap deployments at a minimum between a production and pre-production environment. Microsoft cover in depth what happens when you commence a swap, but what they don’t cover is what happens to any managed identities that you have setup for the app service.
In short, managed identities are tied to the slot in which you first create or assign them, and do not change when you initiate a swap between two or more slots.
You might recall that for an App Service you can have both a system-assigned or a user-assigned identity. These are configured to allow your App Service to access other Azure resources, without the need for sharing secrets and passwords.
When swapping slots, both system and user-assigned identities remain tied to the slot. They don’t swap – so if you need to change these, you’ll need to intervene separately.
Once you’ve generated or assigned an identity, don’t forget to then add it to any Azure resources your app needs access to.
Also keep in mind the lifecycle of a managed identity. User assigned identities won’t be removed whenever you delete a slot. On the other hand, system assigned identities will be deleted as soon as you delete a slot. Depending on your situation, you may prefer one of these approaches.